I was riding with friends but we got bored of the groomed hills so we decided to try out riding in the woods a bit. There was a path about 2 feet wide that went on for a while but I couldn't control my speed at all. I tried tiny skidded turns but that caused me to go off the path. How do I do anything without hitting trees?

Well, if the path is a deep rut and the snow is hard and crusty you're probably SOL. But otherwise, you can brake using only the tail of the board. You basically turn very slightly towards one side then throw the tail against the side of the rut. It's enough to slow you down. To stop you'll basically have to do this more aggressively and climb the side and stop.